Update apollo-graphql to latest 0.2.x version.

This incorporates the changes from:

apollographql/apollo-tooling#1112

...which provides a new `defaultOperationRegistrySignature` function that
will be utilized by both the CLI and this plugin to provide the same
normalization.

Author: abernix

packages/apollo-server-plugin-operation-registry/package.json

@@ -11,7 +11,7 @@
     "node": ">=8"
   },
   "dependencies": {
-    "apollo-graphql": "0.1.2",
+    "apollo-graphql": "0.2.0",
     "apollo-server-caching": "^0.3.1",
     "apollo-server-errors": "^2.2.0",
     "apollo-server-plugin-base": "^0.3.2",